Typical force curves. (A) A typical force versus piezo displacement curve obtained from the measurement, with the approach curve (solid red) and the retract curve (dashed blue). (B) Force versus separation approach curve calculated from the force versus piezo displacement curve. (C) Force to the power of 2/3 versus separation approach curve, showing distinct transition from the tip only sensing the fibril (part I) to the part where the tip is sensing the mica under the fibril (part II) until the part where the tip is only pressing on the mica (part III). From the slope of part I, a modulus of elasticity of 1.2 GPa was calculated for the force curve presented here.